Disable force adding <html>, <head> and <body> tags into the output file when built with custom template

Context: I am using this plugin to make a snippet (using a custom html-lodash template) that will be included in another main html file which already has `<html>`, `<head>` and `<body>` tags set, so I don't need those to be force added into my generated file. 

Suggestions: make it controllable with a boolean setting in configuration, or disable it when using custom template.